Methods and apparatuses for protecting a seal in a pressure vessel of a photolithography system

ABSTRACT

A vessel having a seal that is protected from the liquid material within the vessel by a volume of gas. The vessel has a partition that divides the vessel into two volume spaces such that the seal that is in gaseous communication with the first volume space is protected from the liquid material in the second volume space by a volume of gas in the first volume space.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No. 15/711,678 filed on Sep. 21, 2017 which is incorporated by reference herein.

BACKGROUND

The present invention relates to methods and apparatuses for sealing a vessel. More particularly, the present invention relates to methods and apparatuses for protecting a seal using a captured gas volume.

Pressure is an important parameter in many modern industrial and technological processes. In manufacturing, for example, many fluids may be pressurized for the purpose of transporting, ejecting, spraying, applying force, and the like. In particular, photolithography systems that employ extreme ultraviolet (EUV) light for exposing wafers often generate their EUV light by irradiating molten targets (for example tin targets) with laser light. The molten tin targets are pressurized at a high pressure (typically in the range of thousands of PSI) and delivered from a molten tin reservoir to the irradiation site. In a typical scenario, the tin droplets are ejected out of the nozzle of a droplet generator system. The molten target material delivery system that delivers the molten target material (e.g., tin) from one or more molten target material reservoirs to the droplet generator system often employs one or more pressure vessels in order to help dampen vibration and smooth out the pressure profile during the startup phase, for example. These pressure vessels require seals capable of operating across a wide range of temperatures and pressures. Embodiments of the invention are directed to protecting the seals of vessels such as (without limitation) the pressure vessels employed in the molten target material delivery system of a photolithography tool.

SUMMARY OF THE INVENTION

The invention relates, in an embodiment, to a photolithography system having a molten target material delivery system, the molten target material delivery system delivering molten target material at least from a first location to a second location. The system comprises a vessel disposed in the fluid path between the first location and the second location and in fluidic communication with both the first location and the second location. The vessel includes a vessel wall enclosing at least an inner volume space. The vessel also includes a partition disposed within the vessel wall, the partition dividing the inner volume space into at least a first volume space and a second volume space, the partition configured to permit gaseous communication between the first volume space and the second volume space when no molten material is present within the inner volume space, the first volume space trapping at least a portion of a gas that exists within the first volume space when molten target material is present in the second volume space. The vessel further includes an inlet port and an outlet port, the second volume space being in fluidic communication with both the inlet port and the outlet port. The vessel additionally includes a seal disposed such that the seal is in gaseous communication with the first volume space and the second volume space when the molten target material is absent from the second volume space, the seal being in gaseous communication with the trapped gas within the first volume space and not in gaseous communication with the second volume space when the molten target material is present in the second volume space.

In another embodiment, the invention relates to a photolithography system having a molten target material delivery system, the molten target material delivery system delivering molten target material at least from a first location to a second location. The system includes a vessel disposed in a fluid path between the first location and the second location and in fluidic communication with both the first location and the second location. The vessel includes a vessel wall enclosing at least an inner volume space. The vessel also includes a partition that divides the inner volume space into a first volume space and a second volume space, wherein the first volume space and the second volume space are in gaseous communication when a first quantity of molten target material is present in the second volume space, the first volume space and the second volume space are not in gaseous communication due to being blocked by the molten target material when a second quantity of molten target material is present in the second volume space, the second quantity of molten target material being greater than the first quantity of the molten target material. The vessel additionally includes a seal in gaseous communication with the first volume space.

In yet another embodiment, the invention relates to a photolithography system having a molten target material delivery system, the molten target material delivery system delivering molten target material at least from a first location to a second location. The system includes a vessel disposed in a fluid path between the first location and the second location and in fluidic communication with both the first location and the second location. The vessel includes an vessel wall enclosing at least an inner volume space, the inner volume space including a first volume space and a second volume space, wherein the first volume space and the second volume space are in gaseous communication via a channel when a first quantity of molten target material is present in the second volume space, the first volume space and the second volume space are not in gaseous communication due to the channel being blocked by the molten target material when a second quantity of molten target material is present in the second volume space, the second quantity of molten target material being greater than the first quantity of the molten target material. The vessel also includes a seal in gaseous communication with the first volume space.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which:

FIG. 1 shows, in accordance with an embodiment of the invention, a side view of a pressure vessel having a first pressure vessel subassembly and a second pressure vessel subassembly.

FIG. 2 shows, in accordance with an embodiment of the invention, the pressure vessel of FIG. 1 with molten target material beginning to flow into inner volume space of the pressure vessel.

FIG. 3 shows, in accordance with an embodiment of the invention, the pressure vessel of FIG. 1 with molten target material being flowed into inner volume space of the pressure vessel and reaching the bottom of the partition.

FIG. 4 shows, in accordance with an embodiment of the invention, the pressure vessel of FIG. 1 with molten target material being flowed into inner volume space of the pressure vessel and rising above the bottom of the partition.

FIG. 5 shows, in accordance with an embodiment of the invention, the pressure vessel of FIG. 1 with molten target material being flowed into inner volume space of the pressure vessel and filling one of the inner volume spaces without contacting the seal.

FIGS. 6A and 6B show, in accordance with an embodiment of the invention, an anti-rotation insert comprising protrusions and a female gland comprising recesses.

FIG. 7 schematically depicts, in accordance with an embodiment of the invention, a fluid connection comprising an insert having one or more protrusions and a female gland comprising one or more recesses.

DESCRIPTION OF ONE OR MORE EMBODIMENTS OF THE INVENTION

The present invention will now be described in detail with reference to a few embodiments thereof as illustrated in the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without some or all of these specific details. In other instances, well known process steps and/or structures have not been described in detail in order to not unnecessarily obscure the present invention.

Embodiments of the invention relate to methods and apparatuses for protecting a seal in a vessel. In one or more embodiments, the vessel is surrounded by a vessel wall such that an inner volume space is enclosed. The pressure vessel may be made up of at least two vessel subassemblies. When these two vessel subassemblies mate to create the inner volume space, a seal is employed to render the mating surfaces between the two vessel subassemblies leak-proof.

The inner volume space may include a first volume space and a second volume space, with the first volume space in fluidic communication with the second volume space via a channel. The first volume space and the second volume space may be created by a partition within the vessel, and the channel may for example be located at the bottom of the partition or may for example be created by a through-hole (i.e., via) in the partition. The second volume space is in fluidic communication with an inlet port for receiving a fluid and an outlet port for outputting the fluid that previously entered via the inlet port. When the pressure vessel is empty, the first volume space and the second volume space are in gaseous communication via the aforementioned channel. As a fluid enters the pressure vessel via the inlet port, the fluid begins to fill up the second volume space, and at some point while the fluid level has risen enough within the second volume space, the fluid blocks the channel.

The blocking of the channel prevents gas from the first volume space to be in gaseous communication with the second volume space. Further, when the fluid blocks the channel, gas is trapped within the first volume space. As the fluid gradually fills the second volume space, a quantity of gas remained trapped within the first volume space. The volume of the trapped gas becomes smaller and smaller as pressure increases within the pressure vessel (i.e., within the second volume space and within the first volume space). However, the volume of this trapped gas will be non-zero since there is no escape path for the trapped gas after the channel is blocked. This non-zero volume of trapped gas keeps the seal from coming into contact with the fluid inside the inner volume space and more specifically keeps the seal from coming into contact with any fluid inside the first volume space. When the second volume space is completely filled with the fluid and the fluid flows out of the outlet port, a non-zero trapped gas volume still exists within a portion of the first volume space to continue to separate the fluid from the seal. In this manner, the seal is protected from coming into contact with the fluid, which may contribute to protecting the seal.

In one or more embodiments, the pressure vessel is a component of a molten material delivery system, such as a molten target material delivery system in an extreme ultraviolet (EUV) photolithography tool. To elaborate, the molten target material (typically tin or one of its alloys although any other suitable target material may be employed) is delivered from a reservoir to a droplet generator for creating droplets. The droplets are ejected by a nozzle into an interior of a chamber where they are irradiated at an irradiation site by a laser beam. The droplets may be irradiated by one or more laser pre-pulses and one or more laser main pulses, in one or more variation of the photolithography tool, in order to create a plasma from the droplets and to generate the EUV light for use in photolithography processing of wafers. EUV photolithography tools are known in the art and will not be further elaborated here.

In one or more embodiments, the pressure vessel is a component of the molten target material delivery system and is disposed in between two locations along the molten target material fluid path. The two locations may be, for example, the molten target material reservoir and the droplet generator system, which includes the aforementioned nozzle. These two locations may also represent any other arbitrary two locations along the fluid path between the molten target material reservoir and the nozzle, which is to say the exact location of the pressure vessel along the fluid path is not a limiting of the scope of the invention.

The pressure vessel may be empty prior to commencement of operation and may thus be in a vacuum state or may have some gas in the pressure vessel. Prior to operation of the photolithography tool, one or more gas purge cycles may be performed to ensure gaseous and non-gaseous contaminants are removed from the molten target material delivery system. During the purging operation, one or more purge gases may be employed and the pressure within fluid path of the molten target material delivery system may alternatively be increased and reduced (e.g., to a vacuum or near vacuum state if desired) to perform the purging with one or more purging gases. Once purging is complete, the molten target material may begin to flow from the molten target material reservoir to the nozzle where droplets of molten target material may be ejected toward the aforementioned irradiation site.

Since the pressure vessel (and there may be one or multiple pressure vessels if desired) is disposed between the molten target material reservoir and the nozzle, the molten target material would begin to flow into the inlet port of the pressure vessel during the startup phase as the molten target material travels along the fluid path between the reservoir and the nozzle. This begins the process of filling up the aforementioned second volume space within the pressure vessel. The quantity (and thus volume) of the molten target material within the pressure vessel continues to increase and at some point will block the communication channel between the second volume space and the aforementioned first volume space. At this point, a volume of gas is trapped within the first volume space and is disposed between the seal and the molten target material in the pressure vessel.

As the molten target material continues to fill up the second volume space, pressure within the pressure vessel may increase and may cause the trapped gas in the first volume space to shrink in volume. However because the trapped gas within the first volume space is blocked from being released when the molten target material blocks the communication channel, the trapped gas will continue to have a non-zero volume since the gas molecules of the trapped gas has no escape route. This volume of trapped gas will continue to keep the seal physically separated from the molten target material, thereby continuing to protect the seal even after the molten target material completely fills the second volume space and flows out of the outlet port of the vessel chamber on its way to the nozzle.

During operation, the pressure within the molten target material delivery system may reach thousands of PSI and the temperature experienced by the seal may be at or near the temperature range that causes the molten target material to stay molten (i.e., relatively high temperature). However, since the trapped gas volume within the first volume space keeps the seal physically separated from the molten target material, the seal may be protected to a much greater degree and the useful life of the seal may be significantly prolonged.

The features and advantages of embodiments of the invention will be better understood with reference to the figures that follow.

FIG. 1 shows, in accordance with an embodiment of the invention, a side view of a pressure vessel 100 having a first pressure vessel subassembly 102 and a second pressure vessel subassembly 104. In the example of FIG. 1, pressure vessel 100 is roughly cylindrical in shape although any suitable shape may be employed. For many reasons, including for example ease of manufacture, ease of assembly, ease of maintenance, etc., a plurality of pressure vessel subassemblies may be manufactured and assembled together to create the pressure vessel. Although only two subassemblies are shown in FIG. 1, a pressure vessel may be formed from any number of subassemblies.

Pressure vessel 100 has a vessel wall that includes walls 106, 108, and 110. Wall 106 is part of pressure vessel subassembly 102 while wall 108 (a cylindrical wall in the example of the side view of FIG. 1) and wall 110 are parts of pressure vessel subassembly 104. When assembled together, a seal 120 (in the form of an O-ring in the example of FIG. 1 but may have any other form factor as desired) is disposed between the two subassemblies 102 and 104 to prevent the leakage of gas or fluid. When properly assembled, walls 106, 108, and 110 form a vessel wall that encloses an inner volume space 130.

Wall 110 has an inlet port 122, and wall 106 has an outlet port 124. Inner volume space 130 includes a first volume space 132 and a second volume space 134. A partition 136, which is integrated with or made a part of first pressure vessel subassembly 102, extends in the direction of arrow 138 (in the direction of gravity) toward wall 110, creating a channel 140 that allows gaseous communication between first volume space 132 and second volume space 134 when channel 140 is not blocked.

Seal 120 is disposed such that it is in gaseous communication with first volume space 132 as shown. When there is no molten target material in inner volume space 130, channel 140 is not blocked and seal 120 is also in gaseous communication with second volume space 134 via first volume space 132 and channel 140.

In FIG. 2, when molten target material is flowed into inner volume space 130 of pressure vessel 100 (via inlet port 122), the level of molten target material will rise over time in inner volume space 130. Due to gravity (whether natural gravity or induced gravity such by using centrifugal force), the level of molten target material will rise in the direction of arrow 150 (the direction of arrow 150 itself is against gravity). In the example of FIG. 2, the level currently rests at reference number 152.

In FIG. 3, the level of the molten target material reaches the bottom of partition 136, thus blocking channel 140 and not permitting first volume space 132 to stay in gaseous communication with second volume space 134. Thus a volume of gas is now trapped in first volume space 132.

In FIG. 4, the molten target material continues to be flowed into the interior space of pressure vessel 100, namely into second volume space 134 of inner volume space 130. This causes the level of the molten target material in second volume space 134 to rise higher (in the direction of arrow 150). The addition of the molten target material increases the pressure within the molten target material delivery system in general and within second volume space 134 in particular. The increased pressure also exerts on first volume space 132, causing the trapped gas within first volume space 132 to shrink. However, since there is no escape port for the trapped gas, there remains a finite, non-zero volume of trapped gas between seal 120 and the molten target material. The trapped gas physically keep seal 120 from coming into contact with the molten target material, thereby improving the life of the seal/O-ring.

In FIG. 5, the molten target material fills up the second volume space 134 and flows out of outlet port 124 on its way to the nozzle, for example. The pressure continues to increase to reach the operating pressure threshold (e.g., around 4,000 PSI in an implementation). This pressure continues to shrink down the volume of the trapped gas within first volume space 132. However, there remains a finite, non-zero volume of trapped gas 170 between seal 120 and the molten target material adjacent to the O-ring.

Seal 120 may be made of an elastomer that can withstand the high operating temperature as well as the high operating pressure ranges. In other embodiments, seal 120 may be made of any suitable material such as a metal or even a hybrid material. In yet other embodiments, the seal may take the physical form of a flat sealing washer or any other form. The point is neither the exact physical form for the seal nor its chemical composition is relevant or limiting of the scope of embodiments of the invention herein.

FIGS. 1-5 show a partition 136 protruding downward (toward wall 110), and the partition ends before reaching wall 110. The gap between downward-pointing end of the partition wall 136 and wall 110 creates the aforementioned channel, as has been discussed herein. In other embodiments, the partition may reach all the way to wall 110 and one or more through-holes may be present in partition 136 to form one or more channels to allow gaseous communication between the first volume space (where the gas is trapped) and the second volume space when the molten target material is not present in the pressure vessel.

In the example of FIGS. 1-5, the first volume space 132 has a tapered shape wherein the base (182 in FIG. 1) is wider than the top (184 in FIG. 1) toward where the seal 120 is disposed. This shape is optional and not always required, but the shape does offer advantages in some embodiments. This shape permits the column of trapped gas near top 184 to maintain a relative large separation in the Z direction (see arrow Z in FIG. 3) with relatively little gas volume. Thus, as the trapped gas inside first volume space 132 is pressurized and shrinks in volume, a large separation in the Z direction between the seal and the molten target material may still be maintained even if the trapped gas inside the first volume space 132 is shrunk to only a small percentage of its original volume.

In another embodiment, there are provided apparatuses and methods for reducing rotation between components when installing a fluid connection. The components may be male and female glands. The fluid connection may form part of a lithographic apparatus, for example. A known method of forming a fluid connection (i.e., a connection between parts through which fluid may flow) includes placing a gasket between a male gland and a female gland and bringing the glands closer together to crush the gasket between the glands, thus forming a seal.

The glands may be brought closer together by rotating a tightening nut in a threaded passage within the female gland. However, during rotation of the tightening nut the male gland may undesirably rotate with respect to the female gland due to friction between the tightening nut and the male gland.

Relative rotation of the glands may result in misalignment of the parts that are being connected by the fluid connection, unwanted torque acting on the parts that are being connected and/or damage being caused to the glands. A damaged gland may result in a reduced lifetime of the fluid connection and/or an increased risk of leakage from the fluid connection. One technique of reducing relative rotation of the glands when installing a fluid connection is to provide an insert comprising a protrusion and a female gland comprising a recess for receiving the protrusion in the fluid connection.

FIGS. 6A and 6B schematically depict, in accordance with an embodiment of the invention, an anti-rotation insert 602 comprising protrusions 604 a and 604 b and a female gland 606 comprising recesses 608 a and 608 b. The insert 602 comprises an aperture 610 for receiving a male gland (e.g., 702 in FIG. 7). In the example of FIGS. 6A and 6B, the insert comprises two protrusions and the female gland comprises two recesses. The insert may have a greater or smaller number of protrusions. The female gland may have a greater or smaller number of recesses. In general, the protrusion of the insert and the recess in the female gland are configured to be complimentary shapes such that the protrusion of the insert fits into the recess of the female gland. When the insert has been inserted into the female gland the protrusions are configured to abut against the walls of the recesses such that relative rotation between the insert and the glands is reduced, constrained, or eliminated.

FIG. 7 schematically depicts, in accordance with an embodiment of the invention, a fluid connection 710 comprising an insert 712 having one or more protrusions and a female gland 704 comprising one or more recesses. The male gland 702 comprises a fluid passage 730 that allows fluid to pass through the fluid connection. The male gland 702 is inserted through an aperture of the insert 712. The insert 712 and the male gland 702 are then inserted into the female gland 704. A tightening nut 714 is rotated within a thread of the female gland 704 such that a gasket 716 is crushed between the male gland 702 and the female gland 704, thus sealing the fluid connection. The protrusions of the insert abut against the walls of the recesses of the female gland (as discussed in connection with FIGS. 6A and 6B) during rotation of the tightening nut 714, thereby reducing relative rotation between the male gland 702 and the female gland 704. The insert comprising one or more protrusions and the female gland comprising one or more recesses described and depicted herein advantageously reduces rotation between male and female glands in a fluid connection, thereby improving the quality of the fluid connection and/or increasing the operable lifetime of the fluid connection. Such a fluid connection may exist (but not required to exist) between a fluid line and an inlet port or an outlet port of the vessel of FIGS. 1-5 for example.

While this invention has been described in terms of several preferred embodiments, there are alterations, permutations, and equivalents, which fall within the scope of this invention. For example, while embodiments of the invention is described with reference to a pressure vessel, embodiments of the invention also apply to any two parts that require a seal that is disposed in between to be protected by a gaseous pocket and should be understood to also cover such arrangements. The invention should be understood to also encompass these alterations, permutations, and equivalents. It should also be noted that there are many alternative ways of implementing the methods and apparatuses of the present invention. Although various examples are provided herein, it is intended that these examples be illustrative and not limiting with respect to the invention. 

What is claimed is:
 1. Apparatus comprising: a first coupling subassembly extending in an axial direction, the first coupling subassembly including a fitting arranged at an axial end of the first coupling subassembly; and a rotational coupling element rotatably surrounding the first coupling subassembly and adapted to be engaged with the fitting such that the rotational coupling element is rotatable with respect to the fitting but axially engageable with the fitting to apply an axial compressive force to the fitting, the fitting having a face with a first configuration such that when the fitting is received in a second fitting when the fitting and the second fitting are brought into axial engagement by rotation of the rotational coupling element, the fitting and the second fitting at least partially rotationally engage to inhibit axial rotation of the fitting with respect to the second fitting.
 2. Apparatus as claimed in claim 1 wherein the first coupling subassembly comprises a gland and an insert having an aperture and at least one protrusion, the gland extending through the aperture, and wherein the second fitting has at least one recess arranged and dimensioned to receive the at least one protrusion.
 3. Apparatus as claimed in claim 2 wherein the first coupling subassembly comprises a gland and an insert having a circular aperture and at least one protrusion extending radially with respect to a center of the circular aperture, the gland extending through the circular aperture, and wherein the second fitting has at least one recess arranged and dimensioned to receive the at least one protrusion.
 4. Apparatus as claimed in claim 2 wherein the first coupling subassembly comprises a gland and an insert having an aperture and at least two protrusions, the gland extending through the aperture, and wherein the second fitting has at least two recesses arranged and dimensioned to receive the at least two protrusions.
 5. Apparatus as claimed in claim 2 wherein the first coupling subassembly comprises a gland and an insert having a circular aperture and at least two protrusions extending radially with respect to a center of the circular aperture, the gland extending through the circular aperture, and wherein the second fitting has at least two recesses arranged and dimensioned to receive the at least one protrusion.
 6. Apparatus as claimed in claim 5 wherein an arrangement of the at least the first configuration lacks circular symmetry.
 7. Apparatus as claimed in claim 2 wherein the first rotational coupling element comprises a coupling nut.
 8. Apparatus comprising: a first rotational coupling element; a first fitting adapted to be axially engaged with the first rotational coupling element; a second rotational coupling element; a second fitting adapted to be axially engaged with the second rotational coupling element and with the first fitting; the first fitting having a first configuration and the second fitting having a second configuration, the first and second configurations being such that the first fitting is received in the second fitting when the first fitting and the second fitting are brought into axial engagement by relative rotation of the first and second rotational coupling elements, the first fitting and the second fitting at least partially rotationally engage to prevent axial rotation of the first fitting with respect to the second fitting.
 9. Apparatus as claimed in claim 8 wherein the first fitting comprises a gland and an insert having an aperture and at least one protrusion, the gland extending through the aperture, and wherein the second fitting has at least one recess arranged and dimensioned to receive the at least one protrusion.
 10. Apparatus as claimed in claim 8 wherein the first fitting comprises a gland and an insert having a circular aperture and at least one protrusion extending radially with respect to a center of the circular aperture, the gland extending through the circular aperture, and wherein the second fitting has at least one recess arranged and dimensioned to receive the at least one protrusion.
 11. Apparatus as claimed in claim 8 wherein the first fitting comprises a gland and an insert having an aperture and at least two protrusions, the gland extending through the aperture, and wherein the second fitting has at least two recesses arranged and dimensioned to receive the at least two protrusions.
 12. Apparatus as claimed in claim 8 wherein the first fitting comprises a gland and an insert having a circular aperture and at least two protrusions extending radially with respect to a center of the circular aperture, the gland extending through the circular aperture, and wherein the second fitting has at least two recesses arranged and dimensioned to receive the at least one protrusion.
 13. Apparatus as claimed in claim 12 wherein the first configuration and the second configuration lack circular symmetry.
 14. Apparatus as claimed in claim 8 wherein the first configuration is complementary to the second configuration.
 15. Apparatus as claimed in claim 8 wherein the first configuration and the second configuration lack circular symmetry.
 16. Apparatus as claimed in claim 8 wherein the first rotational coupling element comprises an externally threaded sleeve and the second rotational coupling element comprises an internally threaded sleeve.
 17. Apparatus comprising a first fitting having an insert with a first configuration, the insert being dimensioned to be insertable into an aperture in a second fitting, the aperture having a second configuration which is complementary to the first configuration, the first configuration and the second configuration being such that the insert is not rotatable with respect to the aperture when the insert is inserted into the aperture.
 18. Apparatus as claimed in claim 17 wherein the first configuration lacks circular symmetry.
 19. Apparatus as claimed in claim 17 further comprising a first rotational coupling element adapted to rotate around the insert and to engage with a second rotational coupling element arranged around the second fitting and to apply a compressive sealing force to the insert when engaged with the second rotational coupling element.
 20. Apparatus as claimed in claim 17 wherein the first rotational coupling element has an external thread and the second rotational coupling element has an internal thread and wherein the first rotational coupling element is adapted to engage with the second rotational coupling element by having the external thread engaged with the internal thread. 